This invention relates to the field of efficient high-powered coherent microwave pulse radio frequency energy generators of the electron bunching type.
Heretofore, the generation of coherent microwave high-level energy from electron beams has been accomplished by bunching a high-energy electron beam and then passing the beam through a "slow wave" microwave or radio frequency structure. In this arrangement, the slow wave structure establishes a condition wherein the radio frequency field is closely coupled to the bunched beam and propagates with a velocity slightly less than the velocity of the bunched beam. Under this condition, energy is transferred from the bunched beam to the radio frequency field so that amplification or transducing of applied direct current energy into radio frequency energy occurs. Both oscillator and amplifier devices based on this arrangement exist in the art. The most common examples of this arrangement are the traveling wave tube, the Klystron and similar devices. Some of the more pronounced disadvantages attending these previous bunched beam devices include the need for precisely focused and controlled beams which are inherently limited in size and power delivery capability, the need for a complicated and delicate "slow wave" structure which is also inherently power limited, and a relatively narrow operating bandwidth--typically on the order of a few percent--a bandwidth limitation imposed by the physics of the slow wave structure.
The patent art includes several examples of microwave generating apparatus that are of general interest with respect to the present invention. Included in these are the U.S. Pat. No. 3,178,656 of M. D. Petroff which concerns a microwave amplifying and generating apparatus employing beam bunching and Cerenkov radiation concepts to generate microwave energy--energy in the relatively low power range of seven watts.
The U.S. Pat. No. of I. Kaufman et al, U.S. Pat. No. 3,221,207, also discloses a microwave power generating apparatus, a device of the electron beam variety wherein the electromagnetic deflection of an electron beam into different portions of a waveguide element is used as the microwave energy generating mechanism. The Kaufman invention refines this general concept into a more efficiently controlled arrangement which includes post deflection acceleration of the electron beam and improved beam timewise utilization.
In the patent of C. A. Ekdahl, U.S. Pat. No. 4,596,967, a relativistic electron beam is converted into high-power microwave emission using the Cerenkov radiation related Smith-Purcell effect in combination with a stainless steel azimuthally-slotted cylindrical grating and a copper optical torrodial resonator combination wherein the transmission grating provides signal feedback to accomplish beam bunching and high gain.